Method and apparatus for communicating orthogonal pilot tones in a multiple antenna communication system

Abstract

Methods and apparatus are provided for communicating pseudo-orthogonal pilot tones in a multiple antenna communication system. Data is transmitted in a multiple antenna communication system having N transmit antennas by generating a number of pilot tones for each of the N transmit antennas, wherein the pilot tones for each of the N transmit antennas are pseudo-orthogonal with each other; and transmitting the data on each of the N transmit antennas. The pilot tones are generally embedded in the data. Data is received in a multiple antenna communication system having N transmit antennas by receiving the data on each of the N transmit antennas, wherein the data includes a number of pilot tones for each of the N transmit antennas, wherein the pilot tones for each of the N transmit antennas are pseudo-orthogonal with each other. The pilot tones can be orthogonal in the frequency domain, time domain, spatial domain, or all of them.

We claim: 
     
       1. A method for transmitting data in a multiple antenna communication system having N transmit antennas, said method comprising the steps of:
 generating a number of pilot tones for each of said N transmit antennas, wherein said pilot tones for each of said N transmit antennas are pseudo-orthogonal with each other in a frequency domain and in a space domain; and 
 transmitting said data on each of said N transmit antennas. 
 
     
     
       2. The method of  claim 1 , wherein said pilot tones are embedded in said data. 
     
     
       3. The method of  claim 1 , wherein said generating step uses a binary phase shift keying (BPSK) signal based on a Walsh sequence. 
     
     
       4. The method of  claim 1 , wherein said generating step uses a quadrature phase shift keying (QPSK) constellation and a Fourier transform sequence. 
     
     
       5. The method of  claim 4 , wherein each of said N antennas transmits a row of a Fourier transform matrix. 
     
     
       6. The method of  claim 1 , wherein said generating step generates a pseudo noise (PN) sequence based on a BPSK signal having a cross correlation that satisfies a predefined criteria. 
     
     
       7. The method of  claim 1 , wherein space domains and said generating step employs a p-PSK constellation and a Fourier transform sequence. 
     
     
       8. The method of  claim 7 , wherein each of said N antennas transmits a row of a Fourier transform matrix. 
     
     
       9. The method of  claim 1 , wherein said generating step uses quadrature amplitude modulation (QAM) constellation points and said p pilot tones have a cross correlation that satisfies a predefined criteria. 
     
     
       10. The method of  claim 9 , wherein the predefined criteria is a threshold. 
     
     
       11. The method of  claim 1 , wherein said generating step further comprises the step of generating a number of pilot tones for each of said N transmit antennas that are also orthogonal in the time domain. 
     
     
       12. The method of  claim 11 , wherein said orthogonal pilot tones have a polarization that is alternated. 
     
     
       13. The method of  claim 11 , wherein each of said N antennas have a polarization sequence that is different and orthogonal relative to each of the other antennas. 
     
     
       14. The method of  claim 13 , wherein the polarization sequence for each antenna is responsive to a unique initial state. 
     
     
       15. The method of  claim 14 , wherein a single scrambler is used to generate a single polarization sequence that is used for each of the N antennas. 
     
     
       16. The method of  claim 1 , wherein the pilot tones are simultaneously transmitted. 
     
     
       17. The method of  claim 1 , wherein generating the number of pilot tones includes overlaying a polarization sequence. 
     
     
       18. The method of  claim 17 , wherein the polarization sequence is in a time domain. 
     
     
       19. The method of  claim 1 , further comprising:
 using a set of pseudo noise (PN) generators to generate the number of pilot tones. 
 
     
     
       20. The method of  claim 19 , wherein a member of the set of PN generators is selected depending on a packet length.